Correlation between airway inflammation and loss of deep-inhalation bronchoprotection in asthma.
BACKGROUND
One of the characteristic features of the hyperresponsive airway smooth muscle in asthma is the loss of deep-inhalation bronchoprotection and bronchodilation. The airway of individuals with asthma is also characterized by inflammation.


OBJECTIVE
To evaluate whether the loss of deep-inhalation bronchoprotection is correlated with the degree of inflammation in the asthmatic airway.


METHODS
Eighteen study participants performed 2 methacholine challenges (identical doses), 1 with deep inhalations and 1 without, separated by at least 24 hours. Airway inflammation was evaluated by measurement of fraction of exhaled nitric oxide (FE(NO)) and induced sputum eosinophils.


RESULTS
A significant negative correlation was found between the degree of deep-inhalation bronchoprotection and airway inflammation when measured by FE(NO) (P = .02, r = .54, n = 18) and by percentage of eosinophils (P = .002, r = .76, n = 12). A significant positive correlation was also found between the FE(NO) and percentage of eosinophils (P = .009, r = .68, n = 12).


CONCLUSIONS
Deep-inhalation bronchoprotection was significantly impaired in individuals with greater airway inflammation. This finding suggests that therapy directed at decreasing airway inflammation may promote the recovery of normal deep-inhalation bronchoprotection.
Allen
Nathan D
ND
Division of Respirology, Critical Care and Sleep Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Davis
Beth E
BE
Cockcroft
Donald W
DW
D000328:Adult; D001249:Asthma / Q000276:immunology*; D001944:Breath Tests; D016535:Bronchial Hyperreactivity / Q000276:immunology*; D016085:Bronchoconstrictor Agents / Q000008:administration & dosage; D004804:Eosinophils / Q000276:immunology*; D005260:Female; D006801:Humans; D007249:Inflammation / Q000276:immunology*; D008297:Male; D016210:Methacholine Chloride / Q000008:administration & dosage; D009569:Nitric Oxide / Q000032:analysis; D013183:Sputum / Q000276:immunology*
D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride; D009569:Nitric Oxide